Commercial eel fishermen off the California coast complete an epic humpback whale rescue mission, leaping onto the giant sea mammal's back to cut it free from a line.

"We were coming in from fishing and there was a white buoy that was wrapped around the whale's tail," said the filmer, Nicholas Taron, about the incident, which took place in September. "He was like, splashing on the water's surface."

The crew spotted the whale from about half a mile away and didn't know what it was at first, so they drove over to check it out. "We saw this big old whale tangled up in all that rope."

They then called the coastguard to request help on the whale's behalf, telling them there was a whale tangled as they didn't know how to handle it. But their efforts appeared fruitless.

They thought that if they cut off the buoy off the rope might untangle and the whale could slip free. "That took about an hour and a half," Nicholas said. "That was before anyone got in the water."

But the rope stayed tangled over the whale's back. "That one rope was still holding him down to the ocean floor, and the whole time he was swimming in very tight counter-clockwise circles because all that rope was still attached to the bottom of the ocean."

It looked like nobody was coming and they decided they couldn't leave the whale to die. "That's when we decided to get Sam in the water," Nicholas said.

"He tried once and he didn't succeed, he tried the second time and he didn't succeed. And that video was the third time."

In the clip, Sam leaps into the water, and impressively mounts the whale's back in an attempt to cut it free before the whale further entangles itself.

"Get it, get it before she dives!" Nicholas shouts at Sam, the man attempting to cut the whale free.

"He jumped in, was able to crawl up his back, and right when that whale fluke almost hit the phone out of my hand, that's when Sam had the knife and cut that one rope. And that's when all the rest of the line fell back in the water and the whale swam free."

The whale had apparently been diving a lot at the beginning of their rescue mission but by the end, it understood they were trying to help it out and calmed down, lying and waiting for them to finish.

"This is going to sound super crazy," Nicholas added, "but when the coastguard told us there was nothing else we could do, just let it be, I turned up the volume really loud on the VHF radio and yelled at the whale and told him to listen, and no one else was coming for him, and we're his only hope, and he better lay still and let us do this or else he's going to die. And this is going to sound super crazy but he did."

The footage was filmed by the F/V Persistence crew, who can be found on Instagram at https://www.instagram.com/fv_persistence

F/V Persistence saves entangled whale off central coast CA.